Drying air heat control and moisture removal apparatus



July 30, 1963 H. E. VAN scoYK DRYING AIR HEAT CONTROL AND MOISTUREREMOVAL APPARATUS 5 Sheets-Sheet 1 Filed April 25, 1960 y .5. kw %m mc.w m5 W T Wm A 5 M w H y 1963 H. E. VAN scx JYK 3,

DRYING AIR HEAT CONTROL AND MOISTURE REMOVAL APPARATUS Filed April 25,1960 3 heet 2 I! P 1'? 6! I 7z 1'; 19 H D M 7% 4 i0 10 1; L 5 1 I! m4 w4" .96 a I 7f I '2 5 I6 416/ Pf {I 14 j/ J7 4 1 14 L m LA a INVENTOR 7;?Z By Howard A: VanS qyA' [/13 ATTORIVH July 30, 1963 H. E. VAN scoYKDRYING AIR HEAT CONTROL AND MOISTURE REMOVAL APPARATUS 5 Sheets-Sheet 3Filed April 25, 1960 I N VEN TOR Howard ,5 Van 620;"? B y l HIS ATTORNEYUnited States Patent 3,099,542 DRYING AIR HEAT CGNTROL AND MOISTUREREMGVAL APPARATUS Howard E. Van Scoyk, Dayton, Ohio, assignor to GeneralMotors Corporation, Detroit, Mich, a corporation of Delaware Filed Apr.25, 1950, Ser. No. 24,365 6 Claims. (CI. 3448) This invention relates toa domestic appliance and more particularly to an improved clothes dryer.

In the clothes drying art many attempts have been made at successfuldrying cycle termination using sensible heat thermostats to gauge thedryness end point. However, the prior art devices have not achievedfully satisfactory results and the drying cycle is ended with theclothes either under dried or over dried. Investigation has determinedone cause for this inaccuracy lies in the fact that moisture condenseson the interior surfaces of the dryer during the drying cycle and isreevaporated near the end of the drying cycle. The cooling effect due tosuch moisture reevaporation adversely affects the temperature responsivemeans seeking to sense the dry bulb temperature change which indicatesthe clothes are dry. Further, the prior art dryer control systems haveplaced the thermostats in a position to sense only the temperature ofthe circulating air. But air temperature alone, sensed in a remote partof the dryer, is not truly indicative of the clothes dryness condition.The radiant heat of both the heating means and the tumbling clothesneeds to be considered if the drying cycle is to be terminated when theclothes are properly dried. It is to the solution of these and otherproblems that this invention is directed.

Accordingly, it is a general object of this invention to position adryer thermostat in a position to sense both radiant and conducted heat.

It is a more particular object of this invention to mount the heatercontrols for a clothes dryer on the access door to the dryer.

A further object of this invention is the provision of a drying controlsystem for a fabric tumbling drum having a heater at one end thereof andan access opening at the other end wherein a thermostat is positioned insaid access opening to sense the radiant heat of the heater and thefabric.

Another object of this invention is the provision of a dryer heatercontrol means in outlet air temperature sensing relationship to aclothes tumbling drum and in radiant heat sensing relationship to saidheater and said fabric.

Another general object of this invention is the provision of access doormounted thermostats for recirculating air condensing dryers.

Still another general object of this invention is the provision of anautomatic drying cycle termination system for a clothes dryer in whichthe thermostats are positioned in a location which is relativelyunaffected by the reevaporation of condensed moisture in the dryer airpassage.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIGURE 1 is a schematic perspective view with parts broken away to showthe interior of a vented clothes dryer;

FIGURE 2 is a side sectional view taken through the center of theclothes dryer shown in FIGURE 1; and

FIGURE 3 is a schematic perspective view with parts ice broken away toshow the interior of a recirculating air condensing dryer.

In accordance with this invention and with reference to FIGURES 1 and 2,a vented type clothes dryer is shown generally at 10. The dryer l0includes a control housing 12 having suitable controls for temperature106* and cycle termination 102 and a cabinet 14 which encloses arotatably mounted clothes or fabric tumbling drum 16. The casing 14 iscomprised of a rear wall 18 having air inlet openings 20 and a frontwall 22. For supporting the tumbling drum 16, a rear bulkhead 24 extendsfrom bottom to top in spaced parallel relationship to the rear Wall 18.A drum support shaft 26 is journaled on the bulkhead 24 and carries apulley 28 in the space between the bulkhead 24 and the casing rear wall18. The tumbling drum 16 is formed in a cylindrical shape and includes arear wall 30 ported or perforated, as at 32, for facilitating ingress ofdrying air to the tumbling drum. At the opposite end of the drum anaxially directed collar 34 defines the air outlet or access opening forthe tumbling drum. The opening formed by the collar 34 axially alignswith an opening 36 in the casing front wall 22. Interposed between thedrum collar 34 and the casing opening 36 is a front port plate or drumfront support member 38'. This port plate 38 is fastened in a resilientseal 40 to the casing front wall 22 and has an inwardly extending collar42 which nests in support relationship within the drum collar 34.Suitable felt sealing material 44 is interposed between the port platecollar 42 and the drum ac cess collar 34 to minimize leakage at thispoint from the tumbling drum. The port plate 38 is provided with aplurality of exhaust outlets 46 which open into a front duct or airpassage 48 leading to a blower 50.

Air circulation through the dryer is initiated by the blower 50. Thisblower is driven by a motor 52 which is, in turn, connected through apulley 54- and belt 56 with the drum pulley 28. Thus, the motor 52 isutilized to initiate air flow through the tumbling drum and, at the sametime, to rotate the tumbling drum. The blower 50* shown in FIGURE 2,includes an outlet duct 58 which may be connected to the side or rearwalls of the dryer for connection therefrom with the atmosphere inaccordance with conventional practice.

In the rear wall 30 of the tumbling drum, an annular shoulder 64 isformed to support an annular flexible, noncombustible seal 66 attache-dthereto by a plurality of L- ,shaped brackets 68. The seal 66 engagesthe inside of the bulkhead wall 24 to define a heater chamber 69'between the bulkhead and the rear wall of the tumbling drum. It is inthe annular chamber 69 that a horseshoe-shaped clothes drying heater 70is disposed. To the rear of the heater 70 is a juxtaposed generallyhorseshoe-shaped reflector panel 72 which reflects and radiates heatfrom the heater 7 it through the perforations 32 of the tumbling drumrear wall ino the tumbling chamber. A series of circumferentiallyarranged air inlet apertures 74 are positioned on both sides of thereflecting panel '72 so that air drawn through the apertures 7 4 isdirected evenly over the heater 70 before it enters the tumbling drum.

It is desirable to filter lint from the circulating air as it leaves thetumbling drum. For this purpose an access door is hingedly mounted at 82to the front wall 22 of the clothes dryer and is adapted to close theaccess opening 36 in the dryer casing and support a lint collectinghousing shown generally at 84. The housing 84 includes a perforated wall86 in axial alignment with the port plate collar 42 and the drum inletcollar 34, when the door is closed. The side of the lint collectinghousing is formed by a cylindrical wall 88 fastened at one end thereofto an inner panel 31 of the door and at the other end thereof to theperforated Wall 86. At the top of the housing wall 88 a top opening )0is formed for receiving a lint collector 91. The collector includes afilter means such as a nylon screen 92, and is slidably removable fromthe lint collecting housing 84 through the top opening 90. Along thebottom of the cylindrical wall 88 a cutout 93 is provided to facilitateegress of filtered air from the housing into the front duct 48 by way ofthe port plate openings 46. To facilitate an airtight relationshipbetween the lint collecting housing 84 and the port plate 38, an annularseal 96 is fastened about the periphery of the perforated wall 86. Thuswhen the door 80 is closed, all air leaving the tumbling drum ischanneled through the lint collecting housing 84.

The air flow system defined by the construction outlined hereinabove fora vented clothes dryer is as follows. With the energization of the motor52, both the blower 50 and the tumbling drum 16 are actuated. Air isdrawn through the openings 20 into the casing rear wall and enters theannular heater chamber 69 by way of the inlet openings 74. After beingheated by the heater 70, the air then enters the tumbling drum throughthe perforations 32 in the drum rear wall.

Moisture and lint are entrained in the air from the tumbling moistclothes within the tumbling drum and this moist and lint laden air iswithdrawn from the tumbling drum by Way of the lint collecting housing84. Air enters the housing through the perforated housing wall andfilters through the lint collecting screen 92. Filtered air leaves thelint collecting housing by way of the cutout 93, entering the front duct48 by Way of the port plate openings 46 and is withdrawn by the blower50 for subsequent disposal by way of outlet 58 to the atmosphere.

In accordance with conventional practice, the primary heater 70 iscycled on and off to maintain the interior of the tumbling drum at somedesired temperature. Prior art devices have placed the temperatureresponsive means in areas which are substantially inaccessible forservicing and which do not reflect actual clothes dryness conditions.Thus, .where it is sought to terminate the drying cycle by sensing asudden increase in dry bulb temperature of the exhaust air, as taught inthe patent to Broglie 2,398,880, issued April 23, 1946, the prior artdryers have lacked accuracy. Even where a control thermostat is used anintegrating timer such as taught in Hughes 2,882,610, issued April 21,1959, the cycle termination has been affected adversely by the locationof the control thermostat. The reason for the inaccuracy is believed dueto small amounts of dust and lint which filter into the front ductsystem 48 and become lodged on the interior of the duct walls betweenthe drum outlet and the exhaust outlet. During the drying cycle, thislint absorbs moisture from [the humid air passing thereover. Moisturedroplets also form on the metal surface of the duct Work. Such moisturedroplets and moistened lint are naturally the last thing to dry in thedryer since these are down stream of the tumbling drum 16. Thus, theclothes within the tumbling drum are actually dry prior to the time thatthe lint and dust coated ductwork is dry. Relatively dry air leaving(the tumbling drum is then used to reevaporate the moisture from thelint coating. Such reevaporation produces an air cooling effect whichwill delay the proper actuation of any control thermostat seeking tosense the aforesaid sudden increase in dry bulb temperature, therebycreating a false indication at the thermostat of moisture remaining inthe clothes. Consequently, the dryer heater 70 is not deenergized soonenough or for long enough periods and the drying cycle itself is notterminated until the clothes have over-dried.

For the above reason, this invention contemplates placing the thermostat104 on the inside panel 81 of the door 80 and within the lint collectinghousing 84. In the integrating timer type of automatic drying cycle setforth in the aforesaid Hughes patent, the thermostat 104 may be presetby the temperature control 100 in accordance with the fabric beingdried, i.e., drying temperatures best suited for delicate loadsapproximately 130 F., for regular loads approximately 180 F., and forwash and wear loads approximately 145 F. The thermostat 104 isselectively positioned in the control circuit for the heater 7 0 andacts to provide the correct temperature within the tumbling drum 16. Itis within the purview of this invention to use a plurality ofthermostats on the door, one for each temperature setting desired. Inthis arrangement, the desired thermostat could be switched selectivelyinto the heater circuit.

With reference to FIGURE 2, it should also be noted that the doormounted location for the thermostat 104 positions the thermostat inrelationship to the clothes in the tumbling drum 16 such that radiantheat from the clothes is sensed by the thermostat. This also makes thethermostat more responsive than a thermostat located in the duct workremote from the tumbling drum. Still further, the thermostat is able tosee the radiant heat of the primary heater 70 through the lintcollecting housing performati-ons and the perforations 32 in the rearwall of the tumbling drum. Thus, the door mounted thermostat not onlyresponds to radiant as well as conducted heat, but it is positionedremote from any moisture laden surfaces which might collect lint andadversely effect the dryness end point control system.

The foregoing has been explained in connection with a vented clothesdryer. However, the door mounted location for a dryer control thermostathas been found even more effective in a recirculating air condensingdryer 110, as shown in FIGURE 3. The general construction isapproximately the same as in the vented dryer 10, but the air passedthrough the tumbling drum is continuously recirculated. In explanationof the construction of FIG- URE 3 parts like those in the vented dryer10 will be given like reference numerals. Thus, the dryer includes acasing 14 having a front wall 22 which is closed by a door 80 having alint collecting housing 84 thereon. Within the casing 14 a tumbling drum16 is adapted for rotation and includes a perforated rear wall 30 andanaccess opening in axial alignment with a front port plate 38. Adjacentthe rear wall of the tumbling drum 16 is a rear bulkhead 112 whichdistinguishes over the bulkhead 24 in a vented dryer in that it is notperforated in the area of the annular chamber formed between thetumbling drum and the bulkhead. Thus, a closed chamber is formed by anannular seal (not shown) but substantially like that seal 66 shown inFIGURE 2 and an identical heater 70 is disposed therein. At the outletend of the tumbling drum, perforations 46 in the port plate 38 open intoa front duct 114 which leads to a condensing heat exchanger, showngenerally at 116. The heat exchanger 116 is of tubular design such thatair entering a header 118 is channeled through the tubes 117 to anoutlet header 120 at the other end of the condenser tubes. Moistureforming in the tubes flows by gravity into the outlet header 120 andfrom there through an outlet conduit 122 into a sump pan 124 which maybe periodically emptied through a removable front grill 125.

A blower 126 withdraws air from the tumbling drum through the condenser116 and returns the air to the tumbling drum by way of a recirculatingair return conduit 128 and a return conduit 130 which has an opening 132into the otherwise closed annular chamber adjacent the rear wall of thetumbling drum. Thus, a closed circuit is established between the blower126- and the tumbling drum 16 of the condensing dryer.

To facilitate more rapid condensation of the moisture from therecirculating drying air in the tubes 117, a second blower system isutilized including a cooling air blower (not shown) driven by a belt 133from the motor 127. Air is delivered from this second cooling air systemby way of a duct 134 to the condenser 116 and adapted to blow relativelycool air in counter flow relationship to the condenser tubes 117. Forfurther details on the condensing dryer system shown schematically inthis invention, reference may be had to our copending application SerialNo. 732,573, now Patent No. 3,032,887, which was filed May 2, '1958, andassigned also to the assignee of this invention.

Lint accumulation within the ductwork of the condensing dryer 110 isespecially adverse to the proper operation of a drying cycle controlsystem having thermostats disposed within the ductwork. Since therecirculating air is extremely humid, droplets of condensation aredeposited inside the front duct 114, the condenser i116 and the returnducts or conduits 128 and 130. When the dryer 110 is being controlled byan automatic termination system such as shown in the patent to Broglie,the accuracy of the system depends on accurately sensing the suddenincrease in dry bulb temperature as the clothing reaches its terminationdryness condition. The problem involves the fact that small amounts oflint which become lodged on the interior surfaces of the various ductsin the recirculating system absorb some of the humidity and condensatefrom the circulating air flow. As the clothes become dry, thecirculating air passing over the clothes becomes dry also. Thisrelatively dry air then starts to evaporate the moisture droplets fromthe inside of the duct system, as Well as drying out the slight lintfilm in the recirculating system. A cooling elfect is produced and thiscooling effect is normally reflected in an unwanted extension of thedrying cycle. Such extension causes the clothes to be overdried.

Such cooling effect also impairs the accuracy of an automatic dryingcycle using the integrating timer technique of Hughes. The heatercontrol thermostat, sensing the misleadingly relatively cool air, willmaintain the heater 70 energized longer than is desirable. When theheater is energized in the Hughes system, the timer is deenergized andthe cycle progress interrupted. Thus, the duration of the drying cycleis extended and the clothes overdnied.

As with the vented dryer '10, the control thermostat 104 is positionedin the lint collecting housing on the door 80 of the dryer. Thisthermostat senses the true dryness condition of the clothes since it isnot affected by any moisture condition within the ductwork itself. It isalso disposed in a position to sense the radiated heat from both theheater 70 and the clothes within the tumbling drum. Consequently, acontrol system utilizing door mounted thermostats is far more accurateand the drying cycle is terminated when the clothes are at the properend point dryness.

Since thermostat 104 is carried on the door 80 of either dryer or dryer110, it is necessary that the electrical conduits be supported betweenthe movable door 80 and the fixed cabinet 14. For this purpose afloating conduit carrying hinge 136 is positioned on the door to receiveand support the wires (not shown) leading from the thermostat to theautomatic drying control. For further details relating to this floatingconduit housing 136, reference may be had to a copending application toHaslup, Serial No. 853,151, now Patent No. 3,042,471, filed November 16,1959, and assigned to the same assignee as this invention.

Although the foregoing construction has been explained primarily asdesirable for use with automatic drying cycles, it should be obviousthat the ability of the door mounted thermostats to sense the radiatedheat of both the heater and the tumbling clothes results in a moreresponsive timed drying system. The readily accessible location of thethermostat 104 also enhances the servicing of the appliance. This is animportant factor since a lint or dust coated thermostat will not reflectthe true air condition. Especially is this so when the lint coating is'damp and reevaporating moisture from its surface. The resultant coolingeffect hampers thermostat operation. Aside fro-m the ease with whichthis invention permits cleaning the thermostat, it should be noted thatthe constant opening and closing of the dryer door 86 Will help todislodge any lint and dust from the surface of the thermostat.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In combination, means forming a chamber for tumbling fabric, saidforming means having means including a perforated chamber wall fordefining an air passage through said chamber, means adjacent theperforations of said chamber Wall for heating said chamber, a pivotallymounted door for said chamber, a lint collecting housing on said door,said housing having a perforated housing wall facing said perforatedchamber wall through the interior of said chamber and interposed in saidair plassage when said door is closed, a lint collector in said housingbehind the perforations of said housing Wall for filtering air from saidchamber, temperature responsive means in said housing adjacent theperforations of said housing wall and behind the lint collector and saidhousing wall in straight line exposed radiant heat receivingrelationship to said 'heating means through the perforations of saidhousing wall and said chamber wall for controlling said heating means,and means for inducing an air flow sequentially into heat receivingrelationship with said heating means, into moisture and lint receivingrelationship with said fabric, into lint depositing relationship withsaid lint collector, and into temperature sensing relationship with saidtemperature responsive means.

2. A dryer for moist fabrics comprising a chamber for said fabrics, saidchamber having an access opening, means for closing said opening, meansfor heating said chamber to remove moisture from said fabrics, a lintcollecting housing on said closing means, an air-cooled condenserincluding a plurality of open-ended elongated tubular air passageways,means including a first blower for recirculating drying air through saidchamber into moisture absorbing relationship with said fabrics, throughsaid lint collecting housing and through the interior of said tubularair passageways in series flow relationship, means including a secondblower for circulating cooling air across the exterior of said tubularair passageways to remove moisture from said recirculating drying air,and temperature responsive means on said closing means upstream fromsaid tubular air passageways for controlling said heating means.

3. A dryer for moist fabrics comprising a chamber for said fabrics, saidchamber having an access opening, means for closing said opening, meansfor heating said chamber to remove moisture from said fabrics, a lintcollecting housing on said closing means, an air-cooled condenserincluding a plurality of open-ended elongated tubular air passagewayseach having an inside portion and an outside portion, means including afirst blower for recirculating drying air through said chamber intomoisture absorbing relationship with said fabrics, through said lintcollecting housing and into engagement with one of said portions of saidtubular air passageways in series flow relationship, means including asecond blower for circulating cooling air into engagement with the otherof said portions of said tubular air passageways to remove moisture fromsaid recirculating drying air, and temperature responsive means on saidclosing means upstream from said tubular air passageways for controllingsaid heating means.

4. A dryer for moist fabrics comprising a chamber for said fabrics, saidchamber having an access opening, means for closing said opening, meansfor heating said chamber to remove moisture from said fabrics, anaircooled condenser including a plurality of open-ended elongatedtubular air passageways each having an inside portion and an outsideportion, blower means including a first section for recirculating dryingair through said chamber into moisture absorbing relationship with saidfabrics and into engagement with one of said portions of said tubularair passageways in series flow relationship and .a second section forcirculating cooling air into engagement with the other of said portionsof said tubular air passageways itO remove moisture from saidrecirculating drying air, and temperature responsive means on saidclosing means upstream from said tubular air passageways for controllingsaid heating means.

5. In combination, a fabric dryer including a container having an accessopening and a perforated container wall, a door for closing said openingand having a perforated door Wall adapted to be positioned in saidaccess opening when said door is closed, means for moving said containerto agitate said fabric, means for initiating moisrture absorbing aircurrent through said perforated container wall, said container, and saidaccess opening and said perforated door Wall and including airimpelli-ng means, heating means adjacent the perforations of saidcontainer [Wall and in heat transfer relationship to said air currentsfor heating said air currents to dry said fabric, and enclosed condensermeans having one end connected to said access opening through theperforations of said door Wall when said door is closed and another endconnected to said air impelling means for returning said air currents tosaid air impelling means, said enclosed condenser means being elongatedin a manner whereby air currents moving therethrough are cooled belowthe dewpoint and moisture is condensed from said air current on theinside of said enclosed condenser means, and temperature responsivemeans on said door adjacent the perforations of said door wall andbehind said door Wall upstream from said enclosed condenser means and instraight line exposed radiant heat receiving relationship to saidheating means through the perforations of said container wall and saiddoor wall when said door is closed for controlling said heating means.

. 6. A dryer for moist fabrics comprising a chamber for said fabrics,said chamber having an access opening, means for closing said opening,means for heating said chamber to remove moisture from said fabrics, anaircooled condenser including an open-ended elongated tubular airpassageway having an inside portion and an outside portion, aircirculating means including a first section for recirculating drying airthrough said chamber into moisture absorbing relationship with saidfabrics and into engagement with one of said portions of said tubularair passageway in series flow relationship and a second section forcirculating cooling air into engagement with the other of said portionsof said tubular air passageway to remove moisture from saidrecirculating drying air, and temperature responsive means on saidclosing means upstream from said tubular air passageway for controllingsaid heating means.

References Cited in the file of this patent UNITED STATES PATENTS2,019,011 Johnson Oct. 29, 1935 2,589,284 ONeil Mar. 18, 1952 2,675,628ONeil Apr. 210', 1954 2,769,246 Shapter Nov. 6, 1956 2,814,130 CayotNov. 26, 1957 2,878,580 Hughes Mar. 24, 1959 2,885,789 Conkling et al.May 12, 1959

1. IN COMBINATION, MEANS FORMING A CHAMBER FOR TUMBLING FABRIC, SAIDFORMING MEANS HAVING MEANS INCLUDING A PERFORATED CHAMBER WALL FORDEFINING AN AIR PASSAGE THROUGH SAID CHAMBER, MEANS ADJACENT THEPERFORATIONS OF SAID CHAMBER WALL FOR HEATING SAID CHAMBER, A PIVOTALLYMOUNTED DOOR FOR SAID CHAMBER, A LINT COLLECTING HOUSING ON SAID DOOR,SAID HOUSING HAVING A PERFORATED HOUSING WALL FACING SAID PERFORATEDCHAMBER WALL THROUGH THE INTERIOR OF SAID CHAMBER AND INTERPOSED IN SAIDAIR PASSAGE WHEN SAID DOOR IS CLOSED, A LINT COLLECTOR IN SAID HOUSINGBEHIND THE PERFORATIONS OF SAID HOUSING WALL FOR FILTERING AIR FROM SAIDCHAMBER, TEMPERATURE RESPONSIVE MESNS IN SAID HOUSING ADJACENT THEPERFORATIONS OF SAID HOUSING WALL AND BEHIND THE LINT COLLECTOR AND SAIDHOUSING WALL IN STRAIGHT LINE EXPOSED RADIANT HEAT RECEIVINGRELATIONSHIP TO SAID HEATING MEANS TRHOUGH THE PERFORATIONS OF SAIDHOUSING WALL AND SAID CHAMBER WALL FOR